title: Thioredoxin-family protein EYE2 and Ser/Thr kinase EYE3 play interdependent roles in eyespot assembly.
abstract: The eyespot of the biflagellate unicellular green alga Chlamydomonas reinhardtii is a complex organelle that facilitates directional responses of the cell to environmental light stimuli. The eyespot, which assembles de novo after every cell division and is associated with the daughter four-membered (D4) microtubule rootlet, comprises an elliptical patch of rhodopsin photoreceptors on the plasma membrane and stacks of carotenoid-rich pigment granule arrays in the chloroplast. Two loci, EYE2 and EYE3, define factors involved in the formation and organization of the eyespot pigment granule arrays. Whereas EYE3, a serine/threonine kinase of the ABC1 family, localizes to pigment granules, EYE2 localization corresponds to an area of the chloroplast envelope in the eyespot. EYE2 is positioned along, and adjacent to, the D4 rootlet in the absence of pigment granules. The eyespot pigment granule array is required for maintenance of the elliptical shape of both the overlying EYE2 and channelrhodopsin-1 photoreceptor patches. We propose a model of eyespot assembly wherein rootlet and photoreceptor direct EYE2 to an area of the chloroplast envelope, where it acts to facilitate assembly of pigment granule arrays, and EYE3 plays a role in the biogenesis of the pigment granules.
authors.affiliation: Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ 85721, USA.
authors.forename: Joseph S
authors.initials: JS
authors.lastname: Boyd
authors.forename: Telsa M
authors.initials: TM
authors.lastname: Mittelmeier
authors.forename: Mary Rose
authors.initials: MR
authors.lastname: Lamb
authors.forename: Carol L
authors.initials: CL
authors.lastname: Dieckmann
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002462:Cell Membrane; D016825:Chlamydomonas reinhardtii / Q000235:genetics / Q000378:metabolism*; D002736:Chloroplasts; D015151:Immunoblotting; D008565:Membrane Proteins; D009940:Organoids; D055519:Photoreceptors, Plant / Q000378:metabolism*; D010860:Pigments, Biological; D010940:Plant Proteins / Q000378:metabolism*; D055503:Protein Multimerization; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D015398:Signal Transduction
chemical_list: D008565:Membrane Proteins; D055519:Photoreceptors, Plant; D010860:Pigments, Biological; D010940:Plant Proteins; C438146:eye2 protein, Chlamydomonas reinhardtii; D017346:Protein Serine-Threonine Kinases